The story of the couple who subjected a woman with severe learning difficulties to eight years of depraved sexual and physical abuse in a Craigavon house is truly shocking.

We have read or heard about similar cases previously in Austria and in the US, but it never seemed possible that such behaviour could be happening in a housing estate in Northern Ireland.

Even experienced police officers were astounded by the story that unfolded after a woman finally blew the whistle on Keith Baker and his wife Caroline, who had kept their victim prisoner under appalling circumstances and who, sickeningly, they filmed being subjected to vile attacks.

It was truly a House of Horrors and one wonders how this poor woman's ordeal went unnoticed for so long. She was not known to the authorities here, having been brought over from England by the couple.

What this shows is that we are never certain what goes on behind anyone's closed doors. For those with the deviancy and cunning to commit such a crime, covering their tracks was relatively easy. There was no record of the victim even being here - she had gone missing from her home in England 13 years ago.

It is astounding to realise that Baker and his wife were at one time carers with the Salvation Army. Indeed, there was nothing in Baker's background which suggested that he would descend into such an immoral cesspit.

His behaviour emerged from the darkest recesses of the human mind, and his jail term of 15 years was just deserts for someone who could rightfully be called a monster.

He was described in court as a Svengali-like figure who not only exercised strict control of his wife - making her simultaneously a perpetrator and a victim - but also entranced the woman who was eventually to turn him in to police. She was effectively his second wife and bore him four children.

It almost beggars belief that women who knew of his perversions could nevertheless remain under his control and silent for so long.

The question now in many people's minds is whether there are more people like Baker and his wife out there, preying on the most vulnerable of victims.

Imagine the fears of families who saw a loved one disappear in unexplained circumstances many years ago. Could their missing relative be in the clutches of someone equally perverted? Could there be more 'Houses of Horror' here?